Here is the full list of all 57 Psychonauts 2 achievements. It takes around 25-30 hours to unlock all of the achievements on Windows.
Acquire all Upgrades
Scavenge all MISSION CRITICAL PSYCHONAUTS ASSETS
Purchase all Pins
Max out your PSI Pop capacity
Max out your Dream Fluff capacity
Purchase all Otto Shot Filters
Completely fill your Astral Wallet
Return to where it all started
Tag all Emotional Baggage
Achieve Rank 100
Find all Figments
Crack all Vaults
Complete Lili's Request
Complete Queepie Quest
Complete Gisu's Psychoseismometer Quest
Dissolve the Deluge of Grulovia
Frequent Fatherland Follies
Break all 3 Gramaphones in Fatherland Follies
Soothe Lucrecia's Lament
Peruse Cassie's Collection
Throw a Regret's anvil at another enemy
Empty Bob's Bottles
Discover the Astralathe
Raid the Tomb of the Sharkophagus
Repair Ford Fractured
Bowl Strike City
Achieve Rank 50
Treat Ford's Follicles
Plate Compton's Cookoff
Recover your mental energy with a Dream Fluff
Throw a Judge's gavel back at him
Help Dion Setup Aquatodome
Consume a PSI Pop to restore some mental energy
Upgrade to the Astral Wallet
Find the Family Camp
Deliver Cruller's Correspondence
Complete PSI King's Sensorium
Pyro 3 enemies at once
Find the real Panic Attack during his Phantom attack
Fully upgrade a Badge
Equip 3 Pins at once
Tune in to a Stray Thought
Take a photo with the Otto Shot
Revisit a brain through the Collective Unconscious
Visit the Collective Unconscious
Cool Hollis' Hot Streak
Shut Down the Luctopus
Make a connection in Hollis' Classroom
Achieve Rank 10
Receive your first assignment
Upgrade your first Badge
Talk to Milla in her Office
Equip your first Pin
Achieve Rank 2
Combine PSI Cards with a PSI Core at the Otto-Matic
Navigate Loboto's Labyrinth
TK throw an object to stun an enemy